Can you name the main keywords in Kotlin that are absent in Java?

The main keywords in Kotlin that are not in Java include:

• val and var — for declaring immutable and mutable variables respectively.
• fun — for declaring functions.
• when — an extended version of switch.
• object — for declaring singletons and anonymous objects.
• data — for declaring data classes with automatically generated methods.
• sealed — for creating restricted class hierarchies.
• inline — for indicating functions that are compiled with inlining.
• companion — for declaring companion objects, similar to static members.

These keywords make Kotlin more expressive and concise compared to Java.